1. Field of the Invention
The present invention relates to information record apparatuses and methods such as DVD recorders, and computer program products for making computers function as such information record apparatuses.
2. Description of the Related Art
In order to record data into an information record medium such as a DVD-R or a DVD-RW, the recording operation is performed by making record marks which are formed by irradiating a record surface of the information record medium with a laser beam. A waveform of this laser beam is controlled by a pulse strategy for defining a driving pulse to irradiate a laser beam, so as to record the data appropriately. Furthermore, a recording speed for recording the data into/onto the information record medium becomes faster with development of technologies. For example, 2× recording speed or 4× recording speed is realized.
On the other hand, controlling the waveform (or pulse) of the laser beam for the data recording becomes more difficult, as the recording speed becomes faster. In order to address this problem, the inventor and the like proposed a technology to provide a mid bias period (i.e. a period during which a middle pulse is formed) for a part of the laser beam waveform during a mark period to form a record mark (Japanese Patent Application Laid Open No. 2003-85753). Thus, providing the mid bias period makes it possible to control the laser beam waveform appropriately even at a higher recording speed. A ratio of a laser beam power value during a top pulse period in the mark period except for the mid bias period relative to a laser beam power value during a mid bias period is generally referred to as a “Po/Pm ratio”. When the data is actually recorded into the information record media, the waveform of the laser beam is controlled by a Po/Pm ratio (or an appropriate pulse strategy) predetermined appropriately, for example, by reading a manufacturer code recorded in advance in the information record medium.